Abstract: This study was undertaken to determine whether acetylation of fiber could bring about marked improvement in properties of the hardboard. The pulp was acetyla; ted with 25 per cent (in volume) solution of acetic anhydride in xylene at 125C. The results obtained are as follows: (i) The acetylation of fiber resulted in a obvious expansion in the thickness of the hardboard and the increased dimensional stability is mainly due to the bulking effect. (2) After conditioning.the moisture content of the acetylated hardboard increased slightly. The conversion of cellulosic hybroxyl groups to less hydrophilic acetate groups reduces the amount of water absorbed by the fibers. (3) Swelling in thickness of the specimens in liquid water was cousiderably reduced. The acetylation imparts greater stability to the dimensions of the hardboard. (4) The acetylation does not significantly affect the dry bending strength of the hardboard.